Power control modules

ABSTRACT

A power control module includes a power device having a first side and a second side opposite from the first. The power control module includes a printed wiring board (PWB) spaced apart from the first side of the power device. The PWB is electrically connected to the power device. A heat sink plate is soldered to a second side of the transistor for heat dissipation from the transistor. The PWB and/or the heat sink plate includes an access hole defined therein to allow for access to the transistor during assembly. A method of assembling a power control module includes soldering at least one lead of a power device to a printed wiring board (PWB), pushing the power device toward a heat sink plate, and soldering the power device to the heat sink plate.

BACKGROUND OF THE DISCLOSURE 1. Field of the Disclosure

The present disclosure relates to power control modules and moreparticularly to heat dissipation in power control modules.

2. Description of Related Art

Power control modules, e.g. Solid State Power Controller (SSPC) modules,can be used instead of conventional electro-mechanical relays andcircuit breakers for power distribution in a number of differentapplications. Some SSPC modules are widely used in aircraft secondarydistribution systems. A typical SSPC a power semiconductor device, e.g.a power transistor such as a metal-oxide-semiconductor field-effecttransistor (MOSFET), and control circuitry are typically contained in aprinted wiring board (PWB). A plurality of SSPC modules are oftenassembled onto a common PWB that includes multiple control circuitchannels.

Traditionally, all the power transistors, e.g. MOSFETs, and controlcircuit channels are all on a single PWB. This is convenient forassembly but results in thermal dissipation being limited to whateverthe surface area of that PWB allows for. This also means that the SSPChave been thermally limited to the energy that can be dissipated fromthe PWB. Previous heat sink methods have faced manufacturinginefficiencies due to manual operations required.

Such conventional methods and systems have generally been consideredsatisfactory for their intended purpose. However, there is still a needin the art for improved methods of heat dissipation in SSPC modules,improved methods of manufacturing for SSPC modules with heat sinks, andimproved module assemblies to facilitate such improved methods.

SUMMARY

A power control module includes a power device having a first side and asecond side opposite from the first. The power control module includes aprinted wiring board (PWB) spaced apart from the first side of the powerdevice. The PWB is electrically connected to the power device. A heatsink plate is soldered to a second side of the transistor for heatdissipation from the transistor. The PWB and/or the heat sink plateincludes an access hole defined therein to allow for access to thetransistor during assembly.

In accordance with some embodiments, the access hole is a plate accesshole defined in the heat sink plate to allow for soldering access duringassembly. The plate access hole can be aligned with the second side ofthe power device. The access hole can be a PWB access hole defined inthe PWB. The PWB access hole can be aligned with the first side of thepower device. The PWB access hole and plate access hole can face towardsone another across the power device. The PWB access hole can define acentral axis. The PWB access hole and the plate access hole can bealigned such that the central axis of the PWB access hole extendsthrough the plate access hole. The power device can be electricallyconnected to the PWB by at least one of a drain lead, a source lead or agate lead. The power device can be an ISOTAB transistor. It iscontemplated that the heat sink plate can be a copper plate heat sink.

In accordance with another aspect, a method of assembling a powercontrol module includes soldering at least one lead of a power device toa PWB, pushing the power device toward a heat sink plate, and solderingthe power device to the heat sink plate.

In accordance with some embodiments, soldering includes soldering atleast one of a gate lead, a drain lead or a source lead. Pushing thepower device toward the heat sink plate can include inserting a push pinthrough a PWB access hole and pushing the power device. Soldering thepower device can include accessing the power device with a soldering tipthrough a plate access hole. Pushing and soldering can occur at the sametime. Pushing the power device toward the heat sink plate can includeinserting a push pin through the PWB access hole and pushing the powerdevice from a first side. Soldering the power device can includeaccessing a second side of the power device with a soldering tip throughthe plate access hole. The second side of the power device can beopposite from the first side of the power device.

It is contemplated that the method can include aligning the power devicewith the PWB access hole. The method can include forming the at leastone lead of the power device by bending the at least one lead. Inaccordance with some embodiments, the method includes aligning the PWBaccess hole with the plate access hole. The method can include movingthe PWB and/or the heat sink plate with an automated X-Y table to alignthe PWB access hole and/or the plate access hole with at least one of apush pin or a soldering tip.

These and other features of the systems and methods of the subjectdisclosure will become more readily apparent to those skilled in the artfrom the following detailed description of the embodiments taken inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,embodiments thereof will be described in detail herein below withreference to certain figures, wherein:

FIG. 1 is a schematic side view of an exemplary embodiment of a powercontrol module assembly constructed in accordance with the presentdisclosure, showing a plurality of power control modules each having apower control device (MOSFET) electrically connected to common PWB andmounted to a common copper plate heat sink, where the common PWB andcommon copper plate heat sink are shown in partial cross-section; and

FIG. 2 is a schematic plan view of a top side of an exemplary embodimentof a MOSFET constructed in accordance with the present disclosure,showing drain, gate and source leads.

DETAILED DESCRIPTION

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, a partial view of an exemplary embodiment of a power controlmodule assembly constructed in accordance with the disclosure is shownin FIG. 1 and is designated generally by reference character 100. Otherembodiments of power control module assemblies in accordance with thedisclosure, or aspects thereof, are provided in FIG. 2, as will bedescribed. The systems and methods described herein can be used toimprove heat dissipation and ease of manufacturing of power controlmodules, e.g. Solid State Power Controller (SSPC) modules, such as thoseused in aircraft power distribution systems. The resulting power controlmodule assembly provides about 40% more printed wiring board (PWB) areato accommodate for more power devices, e.g. a single PWB can include40-50 power devices, and can provide improved current limiting duringcurrent inrush events as compared with traditional power control moduleassemblies that have power devices directly mounted on the PWB.Moreover, embodiments of the present disclosure result in about 40% morepower dissipation per module, as compared with traditional modules thatuse the PWB for heat dissipation.

As shown in FIGS. 1-2, a power control module assembly 100 includes aplurality of power control modules 101. Each power control module 101includes a power device 102, e.g. a semiconductor device, such asmetal-oxide-semiconductor field-effect transistors (MOSFETs), having afirst side 104 and a second side 106. Second side 106 is opposite fromthe first side 104 and includes a metallic tab 117 of the MOSFET inlaidtherein. In FIG. 1, metallic tab 117 is shown in the center MOSFET 102,however, those skilled in the art will readily appreciate that the rightand left side MOSFETs, and any others included in the assembly 100 wouldalso have a similar configuration. Each transistor 102 is packaged as anISOTAB MOSFET 102, e.g. where the drain is electrically isolated fromthe metallic tab 117 of the MOSFET 102. Those skilled in the art willreadily appreciate that while transistor 102 is shown and described asan ISOTAB MOSFET, there are a variety of suitable semiconductor powerdevices that may be used for assembly 100. Power control module assembly100 includes a PWB 108 spaced apart from each first side 104 of eachMOSFET 102. PWB 108 is electrically connected to each MOSFET 102 by wayof a source lead 116, a drain lead 118 and a gate lead 120. From theside view of FIG. 1, only gate leads 120 of the MOSFETs 102 are visible.In the view of FIG. 2, however, a respective MOSFET 102 is shown fromits first side 104 and PWB 108 is not shown so that source lead 116, anddrain lead 118 of the respective MOSFET 102 are also visible. Leads 116,118 and 120 are bent upward and out of the page, away from the directionthat an outer surface 115 of the tab 117 of MOSFET 102 faces. This isthe opposite from standard leads, which are typically bent tolongitudinally extend in the same direction that the tab surface faces.Those skilled in the art will readily appreciate that the side profilefor source and drain leads 116 and 118, respectively, would be similarto that of gate lead 120 and would be soldered to PWB 108 in a similarmanner. PWB 108 includes a plurality of control circuit channels, whereeach channel corresponds to at least one of the MOSFETs 102 to form arespective power control module 101.

With continued reference to FIG. 1, assembly 100 includes a heat sinkplate, e.g. a copper plate heat sink 110, parallel to the main PWB 108with all the power MOSFETs 102 mounted on it. Copper plate heat sink 110is soldered to the second side 106 of each MOSFET 102 for heatdissipation from MOSFETs 102. The metallic tab 117 is inlaid within thebottom surface of second side 106 and outer surface 115 of the metallictab 117 faces copper plate heat sink 110. Metallic tab 117 is connectedto copper plate heat sink 110 by way of the solder to dissipate heatfrom the MOSFET 102 to the heat sink 110. This is schematicallyindicated by solder material 105. Copper plate heat sink 110 can becoupled to an aluminum chassis of the assembly by way of a wedge lockcoupling. Copper plate heat sink 110 includes plate access holes 112defined therethrough to allow for soldering access by a soldering tip124 to each respective MOSFET 102 during assembly, which is described inmore detail below. For clarity, a portion of copper plate heat sink 110are broken away and shown in cross-section to show access holes 112 andsoldering tip 124 extending through the middle access hole 112. Eachplate access hole 112 is aligned with a second side 106 of a respectiveMOSFET 102.

As shown in FIG. 1, PWB 108 includes PWB access holes 114 definedtherethrough to allow a push pin 122 to extend through PWB 108 duringassembly. For clarity, a portion of PWB 108 is broken away and shown incross-section to show an access hole 114 and push pin 122 extendingtherethrough. Push pin 122, as described in more detail below, is usedto hold one of the MOSFETs 102 in place against copper plate heat sink110 during soldering. Each PWB access hole 114 is aligned with firstside of a respective MOSFET 102. PWB access holes 114 and plate accessholes 112 approximately face towards one another across their respectiveMOSFETs 102. PWB access holes 114 each define a respective central axisA and PWB access holes 114 and plate access holes 112 are aligned suchthat each central axis A extends through the corresponding plate accesshole 112. While only a single soldering tip 124 and a single push pin122 are shown, those skilled in the art will readily appreciated thatthe automated machinery can operate in a step and repeat operation inorder to solder multiple MOSFETs 102, as described below, or can includemultiple soldering tips and push pins in order to solder more than oneMOSFET 102 to copper plate 110 at a given time. An automatedconfiguration with multiple soldering tips and push pins can alsooperate in a step and repeat operation, e.g. soldering two or moreMOSFETs at a given time and then moving onto another set of MOSFETs.

With continued reference to FIG. 1, a method of assembling a powercontrol module assembly, e.g. assembly 100, includes forming the source,drain and/or gate lead, e.g. source lead 116, drain lead 118 and gatelead 120, of a given transistor, e.g. MOSFET 102, by bending at leastone of the leads toward a PWB, e.g. PWB 108. The method includesprepping the PWB by forming respective PWB access holes, e.g. PWB accessholes 114, for each transistor in the PWB. Those skilled in the art willreadily appreciate that the PWB and its access holes are typicallymanufactured before any assembly is started. The method includesaligning each transistor with its respective PWB access hole. The methodincludes electrically connecting at least one of the leads for each ofthe transistors to the PWB by soldering. Solder material is indicatedschematically by solder 107. A portion of PWB 108 (on the right-handside as oriented in FIG. 1) is shown in cross-section to show the solder107 connection between lead 120 and PWB. Assembly 100, shown in FIG. 1,is assembled by using an automated machine which includes a push pin,e.g. push pin 122, and a soldering tip, e.g. soldering tip 124.

As shown in FIG. 1, the method can include aligning the PWB access holewith its corresponding plate access hole, and/or the method includesmoving at least one of the PWB or the copper plate heat sink with theautomated X-Y table to align at least one of the PWB access hole or theplate access hole with the push pin and/or the soldering tip. AutomatedX-Y table 126 is schematically shown in FIG. 1 and those skilled in theart will readily appreciate that X-Y table 126 may have a variety ofconfigurations to permit movement relative to push pin 122 and/orsoldering tip 124.

Once aligned, the method includes pushing the transistor toward andagainst a copper plate heat sink, e.g. copper plate heat sink 110, withthe automated push pin from a first side of the transistor, e.g. firstside 104. The push pin is inserted through the PWB access hole. Themethod includes accessing a second side, e.g. second side 106, of thetransistor by inserting the soldering tip through a plate access hole,e.g. copper plate access hole 112. While the push pin is pushing thetransistor against the copper plate heat sink from the first side, theautomated soldering tip solders the second side of the transistor to thecopper plate heat sink through the plate access hole. Once the solderingis completed, the soldering tip and push pin are retracted out of theirrespective access holes. Then, an X-Y table, e.g. X-Y table 126, movesthe board to the next location, e.g. the access holes on the PWB andcopper plate corresponding to the next unsoldered transistor. Thepushing towards the PWB and the soldering to the copper plate is thenrepeated for each transistor. Once all of the transistors are solderedto the copper plate, or even in between soldering steps, assembly 100can be cleaned.

This method of mounting the power MOSFETs on copper plate 112 can resultin at least a 40% increase in thermal dissipation by assembly 100 andallows more board area on the PWB for additional SSPC circuit channels.The large shared thermal resource (e.g. the copper plate heat sink)easily consumes thermal transients from lightning and inductive clampingand, due to the increase in thermal dissipation, even allows for shortterm current limiting during inrush and overload events.

The methods and systems of the present disclosure, as described aboveand shown in the drawings provide for power control modules withsuperior properties including increased heat dissipation, more efficientmanufacturing and capability to include more power devices in a module.While the apparatus and methods of the subject disclosure have beenshown and described with reference to certain embodiments, those skilledin the art will readily appreciate that change and/or modifications maybe made thereto without departing from the scope of the subjectdisclosure.

What is claimed is:
 1. A method of assembling a power control modulecomprising: soldering at least one lead of a transistor to a printedwiring board (PWB); pushing the transistor toward a heat sink plate; andsoldering the transistor to the heat sink plate.
 2. The method of claim1, wherein soldering includes soldering at least one of a gate lead, adrain lead or a source lead.
 3. The method claim 1, wherein pushing thetransistor toward the heat sink plate includes inserting a push pinthrough a PWB access hole and pushing the transistor.
 4. The methodclaim 1, wherein soldering the transistor includes accessing thetransistor with a soldering tip through a plate access hole.
 5. Themethod claim 1, wherein pushing and soldering occur at the same time. 6.The method claim 1, wherein pushing the transistor toward the heat sinkplate includes inserting a push pin through a PWB access hole andpushing the transistor from a first side, and wherein soldering thetransistor includes accessing a second side of the transistor with asoldering tip through a plate access hole, wherein the second side ofthe transistor is opposite from the first side of the transistor.
 7. Themethod claim 6, further comprising moving at least one of the PWB or theheat sink plate with an automated X-Y table to align at least one of aPWB access hole or a plate access hole with at least one of a push pinor a soldering tip.
 8. The method claim 1, further comprising formingthe at least one lead of the transistor by bending the at least onelead.
 9. The method claim 1, further comprising aligning the transistorwith a PWB access hole.
 10. The method claim 1, further comprisingaligning a PWB access hole with a plate access hole.
 11. The methodclaim 1, further comprising moving at least one of the PWB or the heatsink plate with an automated X-Y table to align at least one of a PWBaccess hole or a plate access hole with at least one of a push pin or asoldering tip.